Miniaturization is required for the improvement of existing technologies and the enablement of new ones. For example, increases in the speed and processing power of computing machinery are dependent on further miniaturization. Silicon semiconductor devices, are presently fabricated by a “top down” sequential patterning technology using photolithography, far-ultraviolet lithography, or, more recently, electron beam lithography. Although progress with this technology has been made to produce ever smaller devices, it is generally recognized that the reliable production of structures with consistent sub-10 nanometer features probably lies beyond the capabilities of top-down silicon fabrication technology.
Self-assembling nanosystems might create complex and higher density novel device architectures. Such devices could potentially have applications as biosensors, actuators, biomaterials, or nanoelectronic devices for a wide variety of applications in fields as diverse as medicine and material science.
“Bottom up” techniques of self-assembly are common to biological systems (Padilla et al. 2001; Whitesides et al. 2002; Liu & Amro 2002; Lee et al. 2002; Ringler & Schulz 2003). Several companies are developing nanotechnology based on carbon or silicon-based nanostructures, functionalized carbon nanotubes, or buckyballs. An alternative approach to the development of self-assembled nanostructures makes use of biomolecules like nucleic acids and proteins. Several 2-dimensional and 3-dimensional nanostructures formed of DNA have been generated. (Rothemund 2006; Seeman, 2005ab; Shih 2004).
Whole viruses have been used as substrates for nanostructures, as described in Blum et al. (2004), Blum et al. 2005, Chatterji et al. (2004), Chatterji et al. 2005, and Falkner et al. (2005). Cambrios uses virus structures for material sciences applications (www.cambrios.com).
There have been reports of 1-dimensional (e.g. Medalsy et. al., 2008), 2-dimensional (e.g. Sleytr et. al. 2007), and 3-dimensional protein arrays (e.g. protein crystals) have been reported. Padilla et. al (2001) and Yeates et. al (2004) discuss engineered fusion proteins, produced by using recombinant DNA technology to link the genes coding for subunits of protein multimers of different symmetry, and describe the spontaneous assembly in solution of both tetrahedral complexes and a linear helical filament using the fused protein domain approach.
An alternative approach to the formation of 2-dimensional self-assembling lattices of biomolecules involves diffusional organization on self-assembled monolayers (SAMs) (Liu et. al 1996, Liu & Amro 2002, Lee et al. 2002, Sleytr et al. 2007).
The protein-based assemblies cited above primarily result from the spontaneous association of molecules and so only allow limited control over nanostructure assembly.
In 2003, Ringler & Schulz described the formation of a structure that incorporated a modified form of the tetrameric aldolase RhoA from E. coli and streptavidin. They reported the assembly of a 2-dimensional lattice formed of the RhoA tetramers and streptavidin through interaction of the proteins with a self-assembled monolayer.
There are severe limitations in the prior work. For example, the assembly process of Padilla and Ringler & Schulz resulted in the formation of many non-uniform or defective structures with poor quality of the structural assemblies. Because assembly occurred spontaneously, there was no control over the steps of assembly, resulting in partial structures and aggregated complexes. Also, the proteins used in the prior studies were not conformationally stable.